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United States Patent |
5,725,347
|
Hansen
|
March 10, 1998
|
Carousel pin stacker
Abstract
Automation of stacking of lamina included in a modular circuit package is
provided by use of a plurality of heads carried on a preferably rotating
head transport assembly. The head transport assembly is movable between
two locations in which heads simultaneously brought to respective supply,
alignment and disposal stations alternately pick up or deposit lamina,
plates, separator sheets or protective sheets, respectively. Each lamina,
sheet or plate deposited at the alignment station is pressed down over
elongated alignment pins while maintaining only a short protrusion of the
alignment pins above the existing stack. Continuous production is provided
by carousels which bring alignment fixtures to the alignment station and
magazines containing lamina to the supply station. Selection among lamina
is provided by an elevator assembly which moves a magazine to a location
at which a desired lamina can be selected therefrom, preferably under
computerized control. The capacities of the alignment fixtures, magazines,
carousels and supply stations support production of a plurality of stacks
of lamina on an alignment fixture and continuous production of a plurality
of production runs without resupplying the apparatus with lamina or
plates.
Inventors:
|
Hansen; Mark (Orange County, NY)
|
Assignee:
|
International Business Machines Corporation (Armonk, NY)
|
Appl. No.:
|
651192 |
Filed:
|
May 17, 1996 |
Current U.S. Class: |
414/226.03; 29/785; 29/786; 414/806 |
Intern'l Class: |
B65H 039/065 |
Field of Search: |
414/222,223,225,795.8,786
29/771,785,786,709
|
References Cited
U.S. Patent Documents
3553815 | Jan., 1971 | McElvy | 29/786.
|
4113083 | Sep., 1978 | Friese et al. | 414/222.
|
4886592 | Dec., 1989 | Anderle et al. | 414/223.
|
4921397 | May., 1990 | Watanabe | 414/223.
|
4969790 | Nov., 1990 | Petz et al. | 414/222.
|
5174067 | Dec., 1992 | Hasegawa et al. | 414/222.
|
5232505 | Aug., 1993 | Novak et al. | 414/222.
|
5247733 | Sep., 1993 | Kubota et al. | 29/785.
|
5310039 | May., 1994 | Butera et al. | 414/225.
|
5451130 | Sep., 1995 | Kempf | 414/225.
|
5549444 | Aug., 1996 | Dubuit | 414/941.
|
Primary Examiner: Merritt; Karen B.
Assistant Examiner: Hess; Douglas
Attorney, Agent or Firm: Whitham, Curtis, Whitham & McGinn, Ahsan; Aziz M.
Claims
Having thus described my invention, what I claim as new and desire to
secure by Letters Patent is as follows:
1. An apparatus for assembly of a stack of lamina including
a first supply station,
a second supply station,
an alignment station,
a first further station,
a head transport assembly carrying first, second and third heads at
locations allowing simultaneous alignment of said first, second and third
heads with a respective one of said first supply station, said second
supply station, said alignment station, and said further station, and
means for moving said head transport assembly and controlling said first,
second and third heads such that materials at said first supply station
are alternately transported to said alignment station and said further
station and material from said second supply station is transported to
said alignment station between operations for transport of material at
said first supply station to said alignment station.
2. An apparatus as recited in claim 1, wherein said head transport assembly
is rotatable about an axis.
3. An apparatus as recited in claim 1, further including
a first carousel for transporting a supply of fixtures including
registration pins to said alignment station.
4. An apparatus as recited in claim 3, further including
means for aligning one of said fixtures at said alignment station.
5. An apparatus as recited in claim 4, wherein said means for aligning one
of said fixtures at said alignment station includes a robotic cam.
6. An apparatus as recited in claim 4, wherein said means for aligning one
of said fixtures at said alignment station includes alignment pins.
7. An apparatus as recited in claim 4, wherein said means for aligning one
of said fixtures at said alignment station includes alignment bushings on
one of said heads carried by said head transport arrangement.
8. An apparatus as recited in claim 4, wherein said alignment station
includes
a first means for moving a surface to engage an alignment fixture.
9. An apparatus as recited in claim 8, wherein said alignment station
includes
a second means for moving a plate movable on alignment pins of said
alignment fixture to a location proximate a free end of said alignment
pins.
10. An apparatus as recited in claim 9, wherein said alignment station
includes
a third means for raising said alignment fixture against one of said heads
carried by said head transport assembly.
11. An apparatus as recited in claim 10, wherein said second means includes
slip clutch means for supporting said plate and wherein said third means
includes
means for pressing said plate against friction of said slip clutch.
12. An apparatus as recited in claim 1, wherein said alignment station
includes
a first means for moving a surface to engage an alignment fixture.
13. An apparatus as recited in claim 12, wherein said alignment station
includes
a second means for moving a plate movable on alignment pins of said
alignment fixture to a location proximate a free end of said alignment
pins.
14. An apparatus as recited in claim 13, wherein said alignment station
includes
a third means for raising said alignment fixture against one of said heads
carried by said head transport assembly.
15. An apparatus as recited in claim 14, wherein said second means includes
slip clutch means for supporting said plate, and wherein said third means
includes
means for pressing said plate against friction of said slip clutch.
16. An apparatus as recited in claim 1, further including
selection means for selecting a particular one of a plurality of lamina at
said first supply station for transportation to said alignment station.
17. An apparatus as recited in claim 16, wherein said selection means
includes
a magazine for holding respective groups of lamina in accordance with said
plurality of lamina, and
means for moving said magazine relative to said head transport assembly.
18. An apparatus as recited in claim 17, wherein said magazine further
includes
a tray for containing a group of said lamina.
19. An apparatus as recited in claim 16, further including
a carousel for moving a magazine to said means for moving said magazine
relative to said head transport assembly.
20. An apparatus as recited in claim 1, wherein said material at said first
supply station includes lamina with conductive patterns thereon and sheet
means for protecting said conductive patterns and material at said second
supply station includes separator plates.
21. A method of assembling a plurality of lamina from first and second
supply stations on alignment pins of an alignment fixture at an alignment
station, said method comprising the steps of
moving first, second and third heads on a head transport assembly between
first and second positions of said head transport assembly to
simultaneously align said first, second and third heads with a respective
one of said first supply station, said second supply station, said
alignment station, and a further station, and
controlling said first, second and third heads such that materials at said
first supply station are alternately transported to said alignment station
and said further station and material from said second supply station is
transported to said alignment station between transport of lamina at said
first supply station to said alignment station.
22. A method as recited in claim 21, including the further steps of
self-aligning one of said lamina on a tapered end of said alignment pins,
and
pressing said one of said lamina over said alignment pins with a head
carried by said head transport assembly.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to the manufacture of modular
electronic circuits and, more particularly, the automated manufacture of
multi-layer modules (MLM), especially multi-layer ceramic modules (MLC).
2 . Description of the Prior Art
In electronic circuits and high-speed logic circuitry, in particular,
reduction in size and increase in integration and packaging density has
yielded substantial performance improvements due to reduced signal
propagation time over shorter paths and increased noise immunity due to
reduced capacitive and inductive coupling to conductors and other effects.
For this purpose, modular circuits have been in use for several years to
allow connection of numerous integrated circuit chips of diverse types and
formed by different and potentially incompatible technologies within a
single, compact package. Modular circuits also provide advantages of
improved heat dissipation, regulation of temperature among chips,
stability and protection for complex connection arrangements which are
embedded therein and the possibility of electrostatic shielding being
incorporated into the design.
Modular circuits are formed by a plurality of lamina, each having a
conductive pattern formed on one or both sides and perforations, known as
vias, filled with conductive material for making connections between
lamina. Generally, the conductive patterns and filling of vias is
performed by screening of conductive paste through a mask using specially
designed machinery. Each conductive pattern will generally be unique for
each lamina of a modular circuit. The lamina are individually placed in a
stack and carefully aligned with previously placed lamina. Once assembled
and aligned, the lamina are joined by known methods into a unitary body
such as by sintering of uncured ceramic lamina, known as green sheets, or
fusing or bonding of thermoplastic lamina.
Such modular circuits may be extremely complex and require hundreds of
sequentially performed processes (with testing and repair between at least
small groups of steps) to produce. For example, the lamina may be punched
to form an array of vias, screening is done to fill vias and form
conductive patterns (implying that a production run for each unique
pattern will be performed for each required pattern forming a plurality of
identical lamina to be eventually be placed in each of a like plurality of
modular circuits), a covering to protect the pattern and avoid
contamination applied to each lamina, selection and ordering of the
lamina, removal of the covering, placement and alignment of the lamina and
joining of the lamina.
Most of the sequentially performed process steps subsequent to the
screening process must be performed manually due to the requirement for
extremely high alignment accuracy and only small groups of steps have, to
date, been automated. In spite of the substantial expense of such labor
intensive processes, the performance of modular circuits often justifies
the expense since no reasonable alternatives providing comparable
performance and manufacturing flexibility and reliability are available.
The manufacturing process is further complicated by the need for avoidance
of contamination of the lamina while being stacked together and the number
of unique lamina which must be stacked together in a usually critical
order to form the desired connection paths which will be embedded in the
final modular circuit. While so-called clean rooms are well-known and
utilized in many critical manufacturing processes, such clean rooms are
expensive to build and maintain. Further, the presence of personnel
represents an unavoidable source of contamination, as do the activities
carried out in such an environment. Similarly, the possibility of human
error in assembly (e.g. lamina order or alignment during assembly of the
lamina stacks) is also unavoidable. While the possibility of repair (known
as an engineering change or, simply, EC) of modules which may fail tests
performed during the course of manufacture exists and is also provided for
in the design of lamina, a gross error in lamina order or alignment is
unlikely to be repairable; adding to the cost of functional modules
produced.
It has also been the trend in electronic devices that once a new technology
has been introduced and experience gained with manufacturing and design of
circuitry using that technology, the technology is applied to other more
economically accessible devices. The increased performance and
functionality provided by the new technology increases demand for
application of the technology to an increased variety and quantity of
products. By the same token, the increased experience with design and
manufacturing processes tends to increase manufacturing yield and reduce
cost of exploiting the new technology in a wide variety of products.
However, both the compromise of the manufacturing yield and labor costs
attributable to extensive human intervention in the manufacturing process
for modular circuit packages has prevented sufficient reduction in cost of
modular circuits for widespread use of modular circuits at the present
time. Further, production volume is far too limited at the present time to
satisfy demand which would accompany use of modular circuits in a wide
variety of products or even data processors usable as personal computers.
Efforts to accomplish some degree of automation of the assembly process
has not provided for any significant increase in throughput since all
parts of the assembly process must be not only automated but integrated in
order to provide for a continuous assembly and to achieve the needed
increase of production.
It has similarly been a trend in microelectronics that, as a technology
matures, complexity increases within that technology until another
technology is found which overcomes that complexity. While modular
circuits at the present time generally include from five to nine lamina,
it is foreseeable that modular circuits will soon be designed having much
greater numbers of lamina. This projection or expectancy also presents
difficulty for automation of significant portions of the assembly process
since the design and fabrication of machines for automation of the
assembly process is very costly and such a machine might quickly become
obsolete if larger numbers of lamina in a single modular circuit package
could not be accommodated. Likewise and/or alternatively, it is
foreseeable that modular circuit packages could be increased in chip
mounting area to accommodate foreseeable increased complexity, as well,
and there is a trade-off between the cost of larger apparatus for
automation of an assembly process which would accommodate potentially
larger modular circuits including the overhead expense of space to house a
larger apparatus than currently necessary and the cost of a smaller
apparatus which may become obsolete within its service lifetime.
As alluded to above, it is the general practice to make production runs of
each of a plurality of lamina for each required pattern in a modular
circuit design and to store the lamina in accordance with the connection
pattern formed thereon until the lamina are selected in an order specified
by the design, placed in a stack, aligned and joined together into a
unitary, modular structure. Therefore, division of the manufacturing
process between the screening and assembly processes has been the general
practice. However, since alignment has heretofore required manual
performance and is inseparable from the selection and placement
operations, it has not appeared feasible to automate this group of
operations. Uncured ceramic green sheets are also very delicate and
subject to damage during placement and alignment and such delicacy has
hindered efforts at automation of the assembly process.
Further, the number of operations in each of the selection and placement
operations has complicated any attempts to automate any significant
portion of the process. For example, once selection of a lamina suitable
to the sequence in accordance with the design of the modular circuit has
been made, a protective covering must be removed and disposed of. Then the
surface must be cleaned of any contaminant particles which might reach a
surface of the lamina while it is unprotected by covering before placement
and alignment. Additionally, after alignment has been accomplished and
assembly is complete, storage until the lamina can be joined has proven
difficult and to require substantial space, as well as further precautions
against contamination of exposed surfaces.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide automation of
the assembly of modular circuit packages including ordering, cleaning,
placement and alignment of lamina.
It is another object of the present invention to provide for efficient
handling and storage of a plurality of lamina assemblies.
It is a further object of the invention to provide an arrangement which
will provide for continuous assembly of modular circuit packages.
It is yet another object of the invention to provide an arrangement which
will provide for automation of the assembly of modular circuit packages
while reducing the cost of maintaining a clean production environment and,
at the same time, reducing the likelihood of lamina contamination during
assembly.
It is a yet further object of the invention to provide an apparatus for
automation of assembly of modular circuit packages which can accommodate a
plurality of stacks of modular circuit package lamina appropriate to
current modular circuit designs as well as a plurality of production runs
and yet accommodate manufacture of modular circuit packages of increased
numbers of lamina.
It is yet another object of the invention to provide a relatively
inexpensive apparatus for automation of modular circuit package assembly
which can be inexpensively modified to accommodate lamina of greater
dimensions than currently in use.
It is another, further object of the invention to provide for reduced
restriction on the working environment of personnel during assembly of
modular circuit packages.
It is yet another, further object of the invention to provide a compact
arrangement for automating assembly of modular circuits which can,
nevertheless, accommodate the inclusion of many more lamina of
substantially greater area than is currently the practice in modular
circuit design.
In order to accomplish these and other objects of the invention, an
apparatus for assembly of a stack of lamina is provided including first
and second supply stations, an alignment station, a first further station,
a head transport assembly carrying first, second and third heads at
locations allowing simultaneous alignment of the heads with a respective
one of the stations, and an arrangement for moving the head transport
assembly and controlling the respective heads such that materials at the
first supply station are alternately transported to the alignment station
and the further station and material from the second supply station is
transported to the alignment between transportation of material from the
first supply station to the alignment station. While elongated alignment
pins are provided on alignment fixtures for precise registration during
automated stacking, the alignment station provides for maintaining only a
short and constant protrusion of alignment pins above the stack while
supporting the lamina stack along the alignment pins as each lamina is
added.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, aspects and advantages will be better
understood from the following detailed description of a preferred
embodiment of the invention with reference to the drawings, in which:
FIG. 1 is a perspective view of a presently preferred form of the apparatus
in accordance with the invention,
FIGS. 2 and 3 are isometric views of respective forms of the apparatus in
accordance with the invention,
FIG. 4 is a perspective view of a housing for the apparatus of FIG. 2,
FIG. 5 is a perspective view of a housing for the apparatus of FIGS. 1 and
3,
FIG. 6 is a plan view of turntable 140 at a rest position,
FIGS. 6A and 6B are schematic representations of the turntable of FIG. 6,
also in plan view at both the rest position and an active, stacking
position, respectively,
FIG. 7 is a side view of a magazine transport assembly in accordance with
the invention,
FIG. 8 is a plan view of an assembly tray carousel, and
FIGS. 9, 10, 11 and 12 are schematic side views of salient portions of an
alignment station at sequential stages of operation in accordance with the
invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Referring now to the drawings, and more particularly to FIGS. 1-3, there is
shown, in plan view in FIG. 1 and perspective view in FIGS. 2 and 3, the
preferred layout of an arrangement 100 for automating assembly of modular
circuit packages in accordance with the invention. In general, as most
clearly seen in the plan view of FIG. 1, the preferred form of the
invention is laid out in two paths 110, 111 at a 90.degree. angle to each
other. A carousel 120, 130 is located at each of the distal ends of the
paths and a turntable 140 is placed at the juncture of the paths. (The
term "carousel" will be used to connote unidirectional, though
incremental, rotational movement and the term "turntable" will be used to
connote bidirectional rotational movement, in the preferred case through
only 90.degree., corresponding to the angle between the paths.) It should
be understood that the layout of assembly 100 and motion of the carousels
120, 130 and turntable 140 are not critical to the practice of the
invention but are, nevertheless, considered highly preferred and
advantageous to the efficiency and simplicity of design of the invention,
as will be discussed. In particular, the common movement of heads carried
by head assembly 140, regardless of how such movement is achieved, allows
high speed and efficiency of operation to be realized together with high
positional precision of lamina transportation and assembly and removal of
protective material.
It should also be understood that carousel 120, shown in FIG. 3 but omitted
from the embodiment of the invention shown in FIG. 2, is not necessary to
the practice of the invention for modular circuits of current designs but
is, nevertheless, considered highly advantageous for continuous production
and high throughput, at present, and potentially necessary for automated
production of modular circuits having designs of increased complexity
beyond that of current designs. Further, it is to be understood that while
the present invention is considered particularly applicable to assembly of
green sheets into multilayer ceramic (MLC) modules, with respect to which
the invention will be discussed, the invention is not limited thereto but
can be used to advantage with lamina formed of other materials and used to
produce other devices which are assembled from such lamina where high
alignment accuracy and freedom from contamination are important.
The path 110 beginning with carousel 120 supplies lamina to the apparatus
and includes at least one magazine transport assembly 160 for
transportation of a magazine (e.g. 150) containing a plurality of green
sheets having necessary connection patterning in accordance with a
particular modular circuit design. If carousel 120 is included, the
magazine transport assembly 160 includes a portion 170 for horizontal
transportation of a magazine from carousel 120 to a location at which
green sheets are removed therefrom. In either embodiment of the invention,
an elevator portion 180 is provided for moving a magazine 150 vertically
in accordance with the particular green sheet type (e.g. connection
pattern) to be selected.
In both embodiments, a further provision is preferably made for horizontal
transport of a stack of green sheets from magazine 150 toward rotating
head assembly 140 to a location at which they may be more readily accessed
by one of the heads thereon without mechanical interference of a head
(e.g. 605 of FIG. 6) and the magazine transport assembly 160. A preferred
arrangement includes a track 181 and some suitable form of actuator to
move a product tray 182, containing a stack of green sheets, from the
magazine 150 to the location shown in FIGS. 2 or 3.
As noted above, carousel 120 is not necessary to the practice of the
invention and can be omitted. However, inclusion of carousel 120 is
advantageous to continuous production, high manufacturing yield and
accommodation of more complex modular circuit designs since it can provide
for plural magazines to be loaded into the apparatus at a single opening
of a clean enclosure which will be described below for continuous supply
of green sheets or, alternatively, provide for a much increased number of
types of green sheets from which selection can be made, or both.
The path beginning (or terminating) with carousel 130 includes a plurality
of alignment fixtures 190 and provides for a continuous supply of assembly
trays on which MLCs are assembled from lamina and will hereinafter
sometimes referred to as a tray feed assembly. The alignment fixtures
cooperate with an alignment station 195 which provides for exact and
reproducible alignment of the assembly trays with turntable 140 for
stacking of the lamina. The alignment station 195 also provides for
establishing a desired and favorable stacking hole pin depth, preferably
about 0.040 inches, and seating of each green sheet against a previously
stacked green sheet as it is assembled.
The actual assembly of green sheets into MLCs is performed by a plurality
(preferably four) heads mounted on turntable 140, hereinafter sometimes
referred to as a rotating head assembly. The respective heads mounted
thereon, as will be discussed in more detail below, provide the respective
functions of removing protective covering from the green sheets and
disposing of the covering as the green sheets are selected, gripping of
the green sheet and transporting it to an assembly location and picking up
and transporting spacer sheets (2) and plates which allow plural MLCs of
current design to be assembled on a single assembly tray and sintered or
otherwise laminated concurrently subsequent to the operation of the
invention. This important feature of the invention also allows production
of circuit package designs having much increased numbers of lamina than
are needed in current MLC designs but which future designs may require.
All of these functions are provided by the preferred form of the invention
in the course of a single bi-directional excursion of the rotating head
assembly through an angle of 90.degree..
Before proceeding to a discussion of the details of the apparatus 100 of
FIGS. 1-3, it is important to an appreciation of the invention that
automation of the electronic module manufacturing process in accordance
with the invention allows enclosure of the apparatus within an environment
which may be readily, effectively and inexpensively maintained at an even
higher level of freedom from workpiece contamination than a so-called
clean room, in which the apparatus will generally be placed in service.
Specifically, clean rooms require elaborate and expensive air flow and
filtration systems to remove particles and volatile chemicals from the
atmosphere and regulate air flow to a generally vertical direction in
order to trap and/or remove particles and gases over the shortest possible
path before such particles can settle on work pieces being processed by
human workers therein or chemicals affect exposed material surfaces.
However, both machinery and human workers represent sources of contaminant
particles and chemicals. While generation of particles by machines can be
controlled to a substantial extent by placing covers and shrouds around
moving parts, particles and vapors from human workers is much less readily
controllable, even with special clothing and the like. Even movements of
personnel can cause horizontal air currents which may dislodge particles
from a surface and circulate them in the atmosphere. Therefore, separation
of the environment of the manufacturing process to the extent possible
from exposure to human workers will result in much reduced contamination
of the articles manufactured.
Specifically, FIG. 4 shows a suitable enclosure 400 for the embodiment of
the invention shown in FIG. 2 (e.g. without carousel 120). Similarly, FIG.
5 shows an enclosure 500 suitable for enclosure of the embodiment of the
invention shown in FIG. 3. Both enclosures are formed of a framework of
interconnecting elements 401, 501 such as formed tinplate or extruded
aluminum which are arranged to interlock with each other or other pieces
made for the joining thereof, details of which are not important to the
invention. These elements are also preferably formed to support panels
402, 502 and access doors 404, 504 which may be of any suitable material,
transparent, translucent or opaque, which are oriented vertically to
prevent horizontal air currents within the enclosure. Accessories such as
light fixtures 503 and storage cabinets (e.g. 405, 505) are also supported
by the interlocked framework of elements 401, 501. The panels extend as
closely as is practical toward the floor and ceiling and the air currents
developed by the clean room environment, itself, will be much more
effective at removing particles and gases within the enclosure and
separated from human workers. It is preferred to compensate for floor
irregularities and adjust panel proximity to the floor with screw supports
506.
For access to the machine 100 under normal operation, doors 404, 504
provide access to elevator mechanism 180 of the embodiment of FIG. 2 or
carousel 120 of the embodiment of FIG. 3, respectively. Additionally,
enclosures 400, 500 include similar workstations 410, 510, contiguous with
and sharing a common wall with a wall of the enclosure at the termination
of path 111. Access to carousel 130 for inserting alignment plates at
locations 190 thereon and removal of assembled stacks of green sheets is
provided through closeable window 507. The apparatus 100 is preferably
computer controlled and the manufacturing process monitored by computer;
the keyboard and monitor 508 of which may be conveniently located above
window 507. The remainder of the workstation 410, 510 is unimportant to
the practice of the invention but the form shown is considered to be
preferable.
Central to the arrangement and function of apparatus 100 is turntable 140,
shown in plan view at a rest position in FIG. 6 and sometimes referred to
hereinafter as a rotating head assembly or head transport assembly.
Turntable 140 includes a circular base plate 610 pivotably mounted at and
preferably driven from a central shaft 615. Plate 610 also advantageously
carries pneumatic valve banks and pneumatic controllers 630, 640 for
operation of the plurality of heads mounted thereon in order to simplify
and reduce fatigue in connections necessary to control the various heads
of the rotating head assembly. It should also be understood that rotation
is considered to be a highly preferable arrangement for providing common
motion of the heads, particularly when reciprocated as is also highly
preferred. However, neither rotary motion nor reciprocation is
indispensable to the practice of the invention and, for example,
monodirectional rotation or reciprocating linear motion or other common
motion of the heads could be used.
It is important to an understanding of the features of the invention which
will now be explained with reference to FIGS. 6, 6A and 6B to note that
four stationary processing stations 601-604 cooperate with three or four
heads 605-608 mounted on the rotating head assembly or turntable 140. Each
of these heads has a different and specific function. Specifically, green
sheet pick-up head 605 is arranged to pick up a green sheet from a
magazine 150 (FIG. 1) at a supply station 601 and transport it to the
alignment station 602. Plate pick up head 606 performs a similar operation
for separation plates between plate supply station 603 and alignment
station 602. Spacer sheets used for protection of green sheets and
inserted therebetween in magazine 150 or other type of product tray 182
(FIGS. 2 and 3), preferably useable together with magazine 150 to
facilitate extraction from the magazine 150, are removed therefrom by
spacer pick-up head 608 at the green sheet supply station 601 and
transported for disposal at disposal station 604. A similar operation
could be performed between stations 603 and 604 by head 607, if desired
and a suitable head 607 provided.
In FIGS. 6A and 6B, turntable/rotating head assembly 140 is schematically
illustrated in the rest and active positions, respectively as dertermined
at 620 of FIG. 6. The motion of the turntable 140 subsequent to head
operations at these respective positions is shown by arrows A and B,
respectively, whereby all heads are brought to the alternate positions at
which each head performs another action, as may be required.
More specifically, when turntable 140 is at the rest position as shown in
FIG. 6A, green sheet pick up head 605 picks up a green sheet at supply
station 601 while plate pick up head 606 may deposit a separator plate at
alignment station 602, as required, and, in any case, is available as a
mandrel against which green sheets (and separator plates and mylar
separator sheets, if used) may be pressed for relative slight downward
movement of a lamina on alignment pins as will be described in more detail
below and with reference to concurrently filed U.S. patent application
Ser. No. 08/650,078 (Attorney's Docket No. FI9-96-021), which is assigned
to the assignee of the present invention and hereby fully incorporated by
reference. Further, spacer pick up head 608 is in position to dispose of a
protective spacer sheet at station 604 and, if provided, head 607 can pick
up a similar sheet or other object at plate supply station 603 for
transport to disposal station 604. It should be noted that each of these
functions is either completed at the home position or begun at that
position to be completed when the turntable 140 is rotated 90.degree.
(counter-clockwise, as illustrated in FIG. 6A) to an active position which
will now be described.
When turntable 140 is rotated to an active position as shown schematically
in FIG. 6B, green sheet/lamina pick up head 605 is in position to deposit
a green sheet at an alignment station 602, plate pick up head is in a
position at plate supply station 603 to pick up a separator plate from a
stack of similar plates (provision of a six inch stack of ninety-six
plates each 1/16 inch thick is preferred) raised by an actuator (not
otherwise shown) as plates are removed therefrom, if a plate is needed,
and spacer pickup head 608 is in position at product supply station 601 to
pick up a protective spacer sheet from magazine 150 or product supply tray
for return to disposal station 604 when turntable 140 is again rotated
90.degree. in the opposite (clockwise as illustrated) direction to return
to the rest position. If head 607 is provided and had picked up an object
at plate supply station 603, it would be in a position to deposit it at
station 604.
It should be noted that at the active position, heads 606 and 608 can pick
up items at supply stations 601 and 603 while green sheet pick up head 605
deposits a green sheet at alignment station 602 (and, possibly, head 607
deposits an item at disposal station 604). Conversely, at the rest
position heads 606 and 608 deposit separation plates and protective spacer
sheets at alignment station 602 and disposal 604, respectively, while head
605 picks up a green sheet at green sheet supply station 601 from which
the protective spacer sheet has been previously removed. Thus, when viewed
from the standpoint of product supply station 601, a green sheet or a
protective spacer sheet is picked up for each movement of turntable 140
and both are accomplished, transporting green sheets and protective spacer
sheets in opposite directions in a single cycle of movement from the rest
position to the active position and return. Similarly, viewed from
alignment station 602, a green sheet is deposited and either a separator
plate is deposited and/or the most recently deposited green sheet or mylar
separator sheet pressed down in a similar single cycle of turntable
movement from the rest position to the active position and return.
As a perfecting feature of the invention, while a green sheet is in transit
between the home and rest positions, it is possible to further clean the
green sheet by passing it adjacent an air supply nozzle 651 and vacuum
arrangement 650. The pair of air nozzle and vacuum arrangement prevent
particles dislodged from the green sheet from being placed into the
environment atmosphere. Preferably such an air nozzle and vacuum
arrangement are provided for each side of the green sheet.
While turntable 140 is in motion between positions (or before and/or after
such motion, as may be needed), elevator arrangement 180 is activated to
raise or lower magazine 150 to a position at which the next design of
green sheet to be stacked is stored. In the embodiment of FIG. 3, a
magazine which is in use may be lowered onto carousel 120 and carousel 120
rotated to present another magazine which is then lifted to a position
required to access the next green sheet design.
A side view of the elevator assembly (viewed in the direction parallel to
path 110) is shown in FIG. 7. Many of the details shown in FIG. 7 are not
critical to the successful practice of the invention and alternatives will
be apparent to those skilled in the art in view of the following
description just as the function and interaction of many of the details
illustrated will be readily apparent to those skilled in the art and
detailed description thereof is unnecessary. However, the detailed
illustration and the following description are provided as being presently
preferred by the inventor.
Specifically, a track 700 is provided and supported by a stationary frame
such as 701. A moveable elevator assembly includes bearings 702 which
slidably engage track 700, preferably with bearings such as rollers, not
shown, to prevent wear and reduce vibration and lost motion. A
counter-weight system 703 including separate weights 704 and connected to
the moveable elevator assembly at 706 by cable 705 which passes over
pulleys at the top of the stationary frame 701, as shown. The
counterweight assembly 703 is principally intended to balance the weight
of magazine 150 including product trays 182 since the weight of green
sheets and protective spacers as may be contained therein at any time will
be substantially insignificant in comparison. Thus, movement of the
elevator assembly will require little force and the particular actuator
chosen is not important to the practice of the invention. However, a
pneumatic actuator is preferred for ease of control, freedom from
vibration, reduced wear and contaminant materials.
The elevator assembly preferably includes a cantilevered shelf 707 affixed
thereto for supporting a magazine 150. The stationary frame 701 provides
for mounting of proximity or position sensors 708, preferably of the
optical or magnetic type which sense a grid of perforations or other
detectable elements 709' in an element 709 carried by the elevator
assembly. A pawl or detent engaging a preferably saw-toothed surface or
edge of element 709 or another element prevents the magazine 150 from
falling to the level of carousel 120 if power is interrupted. Thus it is
preferred that the pawl or detent be spring biased into contact with the
saw-toothed surface and withdrawn only when positively actuated.
The cantilevered shelf is also preferably provided with a pair of channels
to engage a flanged bottom of a magazine 150 and securely hold it in a
precise location during vertical motion. It is also preferred to provide a
stop plate 711 to further insure correct positioning of a magazine 150,
particularly when it is moved from carousel 120 to the elevator assembly
including shelf 707 by operation of the embodiment of the invention
illustrated in FIGS. 1 and 3. Similarly, it is preferred to provide a
spring-loaded retractable pawl detent 712 to further secure the magazine
150 during vertical motion.
By virtue of the above described magazine transport assembly 160 a magazine
can be lifted to bring a stack of green sheets, each protected by a spacer
sheet to a vertical position corresponding to the heads carried by
rotating head assembly 140. Preferably, as alluded to above, such a stack
of green sheets is contained in a product tray 182 carried by the magazine
150 which can be moved from the magazine on tracks 181 to a location
directly below a head carried by the rotating head assembly. In this way,
mechanical interference between motion of the heads and motion of a
magazine 150 is readily avoided.
The heads 605-608 (FIGS. 1-3 and 6) carried by rotating head assembly 140
are important to the invention to the extent that they must be suitable
for securely gripping a green sheet (or other lamina which are to be
stacked by the invention) while moving it with high precision to another
location without causing any damage to the edges or surfaces (particularly
conductive patterns thereon) of the green sheets. For this reason and the
fact that magnetic and electrostatic pick-up arrangements may not be
suitable for some features possibly included in modular circuit package
designs, a vacuum manifold is preferably attached to commercially
available pneumatic actuators to form the heads for contact with green
sheets, plates, protective spacer sheets etc. Forces derived from vacuum
manifolds for pick-up and pneumatic actuators are readily adjusted by air
pressure supplied thereto and modulated in a well-understood manner to
provide adequately gentle handling of the green sheets and other
materials.
For example, in regard to the actuators, air pressure at about 40 psi. is
preferably used and, given a green sheet area of about 50 square inches
and a three-quarter inch piston, limits pressures applied to about eight
ounces per square inch at the green sheet surface. Variations on the
design of the vacuum manifolds will be apparent to those skilled in the
art and should be provided in accordance with the particular functions to
be achieved by each head.
From the foregoing, it is seen how green sheets are selected in a desired
order by vertical movement of a (selected) magazine 150, protective
spacers removed individually from each green sheet and disposed of and the
green sheet picked up and transported to an alignment station 602 in
accordance with path 110. It has also been demonstrated how separator
plates can be picked up from station 603 and also brought to the alignment
station 602 for stacking with the green sheets. By virtue of the use of
separator plates, plural modular circuits can be assembled vertically and
maintained in that configuration through a sintering process. This process
provides for equalization and uniformity of compressive forces through the
stack of modular circuits during the sintering process and also
facilitates storage and transportation of a greater number of modular
circuits prior to sintering since they are stacked one upon another. The
throughput capacity of the sintering presses and other sintering equipment
is similarly increased. However, the increased height of stacking presents
another problem which is solved by the invention, as will now be
described.
Specifically, if apertures on the green sheets are used for purposes of
precise registration and alignment on pins (preferably four, corresponding
to corners of the green sheet) provided on alignment trays during
stacking, increased stack height requires an increased height of alignment
pins. As the head 605 brings a green sheet to the alignment station and
releases it in substantial registration with the alignment pins, the green
sheet essentially settles on the alignment pins and its motion is
well-described as free-falling or floating since it is not otherwise
constrained.
If the alignment pins are elongated, the likelihood that the green sheet
will assume a diagonal or sloping orientation on the alignment pins is
greatly increased. Such an orientation causes forces to be applied to the
alignment apertures on the green sheet and is likely to cause tearing
thereof. Further, if the green sheets are not individually pressed
together as they are assembled, the potential for contamination is
increased and it is inevitable that air inclusions will result if the
green sheets are only pressed together as a group. Further, and perhaps
more importantly, if the green sheets are pressed together from an angled
orientation, it is inevitable that some wiping motion of one green sheet
against another will result, having the potential effect of smearing the
fine pattern of conductive paste on the surface thereof, potentially
causing massive shorting of conductors and, at a minimum, deforming the
cross-sectional shapes of the conductors. These potential problems and
others are solved by the alignment station, similar to that disclosed and
claimed in the above incorporated, concurrently filed application,
particularly when taken together with carousel 130 in path 111.
Specifically, carousel 130, shown in detailed plan view in FIG. 8, performs
several functions. Most basically, the circumference of carousel 130
allows for a plurality of assembly trays with alignment pins to be
provided and to be ready for stacking of green sheets, as needed, to
provide for continuous production. The diameter of carousel 130 also
provides for physical separation of the alignment station, where the green
sheets are stacked, from the operator to reduce the likelihood of
contamination. After stacking, carousel 130 also returns the stacked
modules to the operator for removal and transfer to lamination press
apparatus.
It should be noted, in this regard, that the size of fixtures 901 is
determined in accordance with the physical transverse dimensions of a
green sheet or other lamina and it is preferred to provide for six
fixtures appropriate to lamina of currently preferred size (e.g. seven to
eight inches on a side) on carousel 130 to provide suitable latitude for
operator activity. Larger lamina could then be accommodated most
inexpensively, if needed, by reducing the number of fixtures 901 on
carousel 130 to four. Alternatively, and preferably, larger lamina could
be accommodated at relatively low expense by increasing the diameter and
circumference of carousel 130 to whatever size is required to hold six
fittings 901 of corresponding dimensions.
Further, the fittings 901 for receiving assembly trays allow the operator
to establish an initial alignment of the assembly trays which is further
refined at the alignment station 602. Specifically, fittings 901 are
preferably sized to provide an alignment accuracy of about 0.005 inches
simply by inserting an assembly tray therein. Alternatively,
micrometer-like screw adjustments could be provided but are not required.
By allowing the operator to bring alignment within certain tolerances that
can be accommodated by the alignment station, the invention can achieve
extremely precise positioning of the assembly trays.
When the assembly tray reaches the alignment station, the alignment pins
are gripped by a template, preferably provided by head 605 or 606, which
can be placed over the tapered ends of the alignment pins or other
mechanism and the latter brought to a precise location. Alternatively,
robotic cams can be used to adjust alignment, as discussed in the
above-incorporated patent application. The assembly tray is then
preferably locked in this precise position by application of a vacuum to
the underside thereof as discussed in the above-incorporated application.
Fixture aligning pins 906 can also be used for either coarse or fine
alignment.
Once precise positioning of an assembly tray is achieved, stacking of green
sheets can begin.
The pressing of the green sheets together as each individual green sheet is
added to the stack is achieved by a frictional linear clutch arrangement
which is more specifically discussed in the above-incorporated U.S. patent
application. But will be briefly discussed herein with reference to FIGS.
9-12 in the interest of completeness.
Essentially, when the stacking fixture 195 (FIG. 1) is brought to the
alignment station 602 (FIG. 6), it will preferably have a stacker plate
902 already fitted over stacking pins 904 by holes sized to readily
provide of movement of stacker plate 902 thereon. Top cylinder 908 then
raises plate 910 to engage the alignment fixture 195 at the vertical
position to which it is brought by the carousel 130 and fine alignment is
carried out.
Referring now to FIG. 10, a middle cylinder 920 (omitted for clarity from
FIG. 9) presses shaft 935 or other suitable linkage upward through a
linear friction slip clutch 930 which, in turn, raises a platform 945
(which may be of annular form if needed for clearance from upper cylinder
908) to raise rods 940 through apertures 950 in plate 910 to lift stacker
plate 902 to a position near the top (preferably proximate a tapered
shoulder portion as discussed in the above-incorporated application) of
alignment pins 904, effectively shortening the pins so that no significant
diagonal positioning of the green sheet can occur to cause tearing or
wiping action. The stacking plate is held at this location by friction
slip clutch 930.
Then, as the rotating head assembly is rotated, head 605 brings a green
sheet into substantial registration with the alignment pins 904 with a
small clearance (preferably about 1/16 inch) above them. As shown in FIG.
11, the green sheet 1000 is then released and allowed to settle on the
shoulder of the registration pins at the juncture of cylindrical and
conical portions thereof, as discussed in the above incorporated patent
application. The head 605 remains briefly in position above the alignment
pins (or head 606 brought to that position) while the lower cylinder 960
raises the upper cylinder 908 and the stacking fixture including the
alignment pins, as shown in FIG. 12. Head 605 or 606 may be allowed to
have small horizontal motion to self-align alignment bushings 970 with
alignment pins 904 during this operation as the alignment pins are raised
together with the alignment fixture 195.
The most recently placed green sheet 1000 rises with the alignment pins
until it contacts head 605 or 606 where it remains in fixed position while
previously placed green sheets (or stacker plate or a separator plate) in
the stack are raised against it, pressing all green sheets, separator
plates and the stacker plate down the alignment pins against the action of
the friction clutch 930. Thus when lower cylinder 960 is returned to the
normal position, the most recently placed green sheet 1000 will assume the
position previously occupied by the previously placed green sheet and the
protrusion of alignment pins 904 above the stack will be precisely
maintained. This operation can be repeated at will to the capacity of the
alignment pins 904.
As the process is repeated, each subsequently stacked green sheet is evenly
and gently pressed against a previously stacked green sheet or plate in
the stack. Further, as each green sheet is added and pressed down by the
head 605 or 606, support rods 940 will be pressed lower through friction
clutches 930 by precisely the thickness of the added green sheet, as
indicated with particular clarity by movement of exemplary piston 980 of
middle cylinder 920. Thus, tearing of the green sheets by the alignment
pins and wiping actions between green sheets is avoided while each green
sheet is pressed against the stack as it is added in order to avoid air
inclusions and to reduce the possibility of contamination.
After the required sequence of green sheets has been stacked, a separator
plate can be added to the stack by head 606 (both preferably under data
processor control) and the process can be repeated to form another module.
(Mylar separator sheets are preferably added to the stack before and after
each separator plate to prevent contact between a lamina and a plate.) It
should be noted in this regard that plural stacks can be formed on the
same stacking fixture 195 by separating them with separator plates
supplied from plate supply station 603. In theory with the alignment
station arrangement described above, there is no limit to the length of
the alignment pins and the number of modules which can be assembled on a
single assembly tray. However, in practice at the present time, it is
preferred to limit the alignment pin height to about 0.85 inches as an
incident of current lamination press dimensions and having nothing to do
with the operation or successful practice of the invention or the
alignment station thereof. Such a practical and conservative alignment pin
height can accommodate about five to ten modular circuits of current
design complexity, allowing a five -to ten-fold reduction in storage space
and a five- to ten-fold increase on lamination press apparatus throughput.
By the same token, a five- to ten-fold increase in complexity (in terms of
number of green sheets required; the number of potential connections
should increase exponentially) over current designs could be accommodated
by the invention.
It should also be appreciated that the invention allows very rapid green
sheet selection, removal of protective spacers, cleaning of particles
during transport, registration and pressing of each green sheet as it is
stacked in very rapid sequence, allowing several modular circuits to be
assembled with high manufacturing yield in a time comparable to the manual
alignment and placement of a single green sheet in a stack. Considering
that the invention provides for continuous production of modular circuits
and other laminated structures while reducing the likelihood of
contamination in a much less labor intensive fashion, the throughput of
the invention together with increased manufacturing yield is far greater
than could be achieved manually. For purposes of comparison, at the
present time the invention is capable of stacking one sheet every 6.8
seconds on a continuous production basis with much increased manufacturing
yield over manual methods whereas manual placement of a single sheet would
often exceed one minute. An operator need only use the time for the
machine to stack 30-50 green sheets and separator plates (a few minutes)
to remove a completed stack from carousel 130 and to replace the assembly
tray/stacking fixture 195 with an empty assembly tray.
In view of the foregoing, it is clearly seen that the invention provides
for continuous automated production of multi-layered modular circuits
including selection, cleaning placement and alignment of lamina while
disposing of protective materials and providing stacking of plural such
circuits for lamination, increasing efficiency of handling and storage as
well as the lamination process itself. Manufacturing yield is increased
and costs of maintaining an adequately clean environment while reducing
contamination of lamina during the stacking process while reducing
restriction on the working environment of a reduced number of assembly
personnel. The apparatus also efficiently provides for accommodation of
far more complex modular circuit designs than are currently in use while
providing substantial manufacturing benefits as applied to current
designs. The apparatus can also be readily and inexpensively modified to
accommodate green sheets or lamina of any practical size.
Further, in view of the fact that a job run is generally on the order of
twenty stacks, each of which can be diced into, for example, nine or
twelve modular circuit packages, and the capacity of the machine for green
sheets, separator plates and the like will accommodate production of
eighty pieces or stacks, it can be seen that four job runs can be
performed without reloading the machine, thus reducing the possibility of
contamination to a very low level. When it is considered that a stack of
lamina for a current modular circuit design will consist of five to ten
sheets and that a stack, once laminated, will be diced into nine or twelve
modular circuits, a stacking rate of 6.8 seconds per sheet in continuous
production translates into an average production of a modular circuit
every 3 to 7 seconds at extremely high production yield and under the
control of a single operator. Therefore, it is clear that the invention
provides for very high volume production particularly when the complexity
and precision of the modular circuit package is considered. It is also
worthy of note that while the apparatus according to the invention is
complex, the tooling cost thereof is only 10%-15% of the tooling required
to support manual assembly in accordance with known assembly methods.
While the invention has been described in terms of a single preferred
embodiment, those skilled in the art will recognize that the invention can
be practiced with modification within the spirit and scope of the appended
claims.
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